The camera of this invention includes an improved shutter system that has a single-speed shutter system and preferably a two step exposure system.
Typically, a camera has a shutter system that permits light to enter the camera to expose the film to light reflected from an object whose picture is being taken with the camera. The shutter system may include a shutter blade that is pivotally mounted to the camera over a shutter opening. The film is disposed behind the shutter opening. In order to expose the film, the shutter blade moves from a closed position, in which it covers the shutter opening, to an open position, in which it uncovers the shutter opening. The shutter blade will then return to its closed position.
As is generally known, shutter systems function to control the amount of light to which the film is exposed. Although a variety of shutter systems have been designed, they can be broadly classified as either a manual or automatic type of shutter system.
In a manual type system, the camera user operates a manual switch to select a desired exposure level or shutter speed. Alternatively, a camera may employ an automatic system that has a magnetic switch for setting the exposure level based on the sensing of the ambient light level.
While both of these systems work well, they each have their drawbacks. The manual type system cannot have an xe2x80x9cautoflashxe2x80x9d feature. A drawback of th automatic system is that it is relatively expensive and, is therefore, not practical for relatively low cost cameras.
Typically, cameras transmit light through different size apertures or vary the shutter speed in order to expose the film depending on whether the camera flash is being employed. Moreover, some cameras have a variable aperture that can be varied in size, so that an optimum aperture size can be selected based upon the lighting conditions. Instead of varying the aperture size, the shutter speed can be varied in order to expose the film depending on whether a flash is used. A relatively fast speed could be employed with the flash, and a relatively slow speed could be employed without the flash.
Single-speed shutter systems are, typically, inexpensive. Thus, some shutter systems employ a single-speed shutter in order to reduce the cost of a camera. However, a single speed design has not yet been developed that satisfies all of the requirements of indoor and outdoor photography.
The camera of this invention has an improved single speed shutter system that is relatively inexpensive, but is able to operate effectively in a wide range of lighting conditions.
The camera of this invention has an improved shutter system that has substantially the same shutter waveform when a flash is employed and when a flash is not employed. Preferably, the camera of this invention has a fixed single-speed shutter and a two step exposure system. The two step exposure system may in one embodiment, include two lens apertures of different size through which light is transmitted when the picture is taken. In a preferred embodiment, the film is exposed to light through the larger lens aperture for about 2 msec. and the smaller lens aperture for amount 10 msec. The flash, if used, is triggered so that the larger lens aperture transmits light from the flash. A light sensing circuit or auto flash feature may be employed to enable the flash to fire when ambient conditions have a relatively low light level. When taking a picture in relative low ambient light conditions, such as indoors, the large lens aperture allows sufficient exposure of the film with the limited amount of light from the camera flash. In contrast, when taking a picture in relatively high ambient light conditions, such as outdoors, the smaller lens aperture provides for better depth-of-field and matches the exposure level to the ambient conditions.
Although exposure through the smaller lens aperture is preferred for non-flash pictures and exposure through the larger lens aperture is preferred for flash pictures, exposing the film through both apertures, whether or not a flash is employed, does not significantly degrade the quality of the exposure. Therefore, this two-step exposure system provides a relatively economical shutter system that produces good quality exposures over a wide range of lighting conditions. More specifically, when the flash is not employed, only daylight travels through the aperture. As the film is exposed to light traveling through the smaller aperture, good lens performance and depth of field is achieved. Although exposure through the larger aperture is not preferred when the flash is not employed, the relatively small exposure time through the larger aperture does not significantly degrade the photograph. Moreover, when pictures are taken with the flash, the film is first exposed through the small aperture to ambient light and when the flash fires the film is exposed to light from the flash through the large aperture. Although exposure through the smaller aperture is not preferable when the flash issued, this exposure through the smaller aperture does not contribute significantly to the overall exposure of the film. Thus, the camera of this invention has a two step exposure system that provides good quality photographs when a flash is employed and not employed and is relatively economical.
The camera in which this improved shutter system is employed may include a main body on which various components of the camera are disposed and that is enclosed by a camera casing. The camera may further include a film cassette compartment, disposed on one lateral end of the camera, and a film spool mounted on the other lateral end. A film cassette can be received into the film cassette compartment, and film may be preloaded by winding the film around the film spool prior to exposing the film. A film path is disposed between the film cassette compartment and the film spool.
A shutter opening is disposed within the main body. Light is transmitted through the shutter opening to expose the film within the film path. A shutter blade is rotatably mounted to the camera and mechanically coupled to a striker. The striker is linked to the picture taking mechanism. The shutter blade is rotatable from a covered position, in which it covers the shutter opening to prevent light from being transmitted through the shutter opening to expose the film, to an uncovered position, in which the s utter opening is uncovered and light is permitted to enter the shutter opening to expose the film. When a picture is taken with the camera, the striker causes the shutter blade to rotate from the covered position to the uncovered position and back to the covered position. Preferably, the shutter blade rotates at the same speed when a picture is taken with or without a flash.
A plate may be coupled to the main body, so that it can move between a first position and a second position, in response to movement of the shutter blade between the covered position and the uncovered position. The plate may have an aperture that defines a first aperture and a second aperture through which light can be transmitted to expose the film. Preferably, the first aperture has a smaller cross sectional area than the second aperture. In its first position, the first aperture is disposed over the shutter opening, so that light is transmitted through the first aperture to the shutter opening. Conversely, in the second position, the second aperture is disposed over the shutter opening, so that light can be transmitted through the larger second aperture and shutter opening.
When a picture is taken with the camera, the shutter blade moves from the covered position to the uncovered position. As the shutter blade is moving and the shutter opening becomes uncovered, light is transmitted through the first aperture and the shutter opening to expose the film. Eventually, the movement of the shutter blade causes the plate, which is responsive to the movement of the shutter blade, to slide so that the second aperture of the plate is disposed over the shutter opening. In this position, light is transmitted through the larger second aperture. As the shutter blade moves back to its covered position, the plate moves back to its first position to expose the film to light through the smaller first aperture.
The blade and the plate move in the same sequence and at the same speed when the flash is employed and when the flash is not employed. Preferably, the first and the second apertures are sized, so that when a flash is employed and when a flash is not employed, the film is exposed to a sufficient amount of light to expose the film, but not so much light so as to degrade the quality of the exposure.
The camera further has a pair of flash contacts that are coupled to the flash and an electrical circuit that triggers the flash. The contacts have a closed position and an open position. In the closed position, the contacts provide power to the flash, and in the open position the contacts interrupt power to the flash. The contacts are preferably normally open and are mounted to the main body of the camera. The contacts are responsive to movement of the shutter blade so that the contacts move from the open position, when the shutter blade is in the covered position, to the closed position, when the shutter blade is in the uncovered position. The shutter blade may physically contact the contacts and push the contacts to the closed position.
In a preferred embodiment, the camera further comprises a lever coupled to the slidable plate and the pair of flash contacts. The lever may be rotatably mounted to the camera and rotatable between a first position and a second position. The ever resides in the first position before a picture is taken and when the small aperture of the slidable plate is disposed over the shutter opening. When the shutter blade rotates it preferably contacts the lever to cause the lever to rotate and thereby move the slidable plate to its second position. As the shutter blade returns to its covered position, the shutter blade rotates back to its first position. As the lever rotates, the slidable plate returns to its first position.
In an alternative preferred embodiment of this invention, the slidable plate is engaged with the flash contacts. In this embodiment, at least one of the flash contacts is flexibly mounted to the camera, such that this flash contact is fixed at one end and free at another end. The shutter blade contacts the free end of the flexibly mounted flash contact, so that this free end of the contact deflects when the shutter blade contacts it. If the slidable plate is mounted to the free end of the contact, the slidable plate moves with the movement of this flexibly mounted contact. The slidable plate moves from its first position to its second position as the contact moves in response to activation by the shutter blade. Upon the shutter blade returning to its covered position, the flash contact rotates and thereby moves the slidable plate to its first position.
Other features of the invention are provided below.